There is some rust in the trunk that I didn't get to. The trunk is also not painted. There used to be rust at the bottom of the door panels, but I sanded it away, used some rust reformer and patched it up.
The original colour was cosmosblau, but it was really badly faded and the clearcoat was almost gone, so I painted it the colour that I always wanted
Under the car, it should be okay. I've had it on jacks a few times and haven't noticed any rust issues there.